Abstract

Venomous animals and their venoms have intrigued mankind for millennia. Venoms are complex cocktails of chemically diverse
components that disrupt the physiological functioning of the victim to aid the venom‐producing animal in defence and/or feeding.
Despite evolving independently on at least 30 occasions in the animal kingdom, venom exhibits remarkable evolutionary convergence,
both in composition and biochemical activity. Various factors, including geography, diet, predator pressure, evolutionary
arms race and phylogenetic history, underpin the diversification of venoms. Certain venomous animals, particularly snakes,
are medically important and are responsible for tens of thousands of permanent loss‐of‐function injuries and deaths in humans
every year. At the same time, as venom harbours many bioactive and highly specific components, it has tremendous potential
applications in the development of novel lifesaving therapeutics and environment‐friendly agrochemicals. Several wonder drugs
based on venom proteins have saved millions of lives worldwide, and many others are in development.

Key Concepts

Venom has evolved independently ∼30 times in the animal kingdom to assist the venom‐producing animal in self‐defence and/or
prey capture.

A remarkable convergence can be observed in the composition and bioactivity of venoms.

While most animals modified their salivary glands into venom glands, the duck‐billed platypus and echidna evolved venom glands
through the evolutionary tinkering of sweat glands.

Cnidarians evolved peculiar cell types to inject venom into their victims, while many hymenopterans have modified their ovipositors
for venom injection.

The strong influence of positive Darwinian selection has driven the evolutionary diversification of venoms, while the structural
integrity is conserved by purifying selection.

Figure 1.Parallel origins of animal venom. The tree of life, based on Casewell et al. (), is depicted here, indicating the multiple origins of venom in animals. Venoms used for defence, predation or intraspecific competition are indicated in blue‐, red‐ and orange‐coloured branches, respectively.

Figure 5.Diverse mechanisms of venom delivery in the animal kingdom. This figure portrays venom delivery in (a) duck‐billed platypus and its spur and (b) vampire bat with incisors and the tongue.

Figure 6.Molecular evolution of venom. This figure describes the homology model of elapid three‐finger toxins, where positively selected sites are indicated in red. A colour code is provided to depict selection pressures experienced by other residues. A sequence alignment has also been provided, where the signal and mature peptides are indicated, along with the sites that exhibit greater than 90% sequence identity (blue) and those that experience positive selection (red).

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